Fuel and feedwater-monitoring system of a once-through steam generator

Abstract

Monitoring system for a once-through steam generator for determining deviations between the amount of heat absorbed by the water and the steam of the generator and the amount of heat given off by a firing system for the generator during operating conditions that are not steady-state, as compared to steady-state operation, includes a first computing circuit responsive to a signal corresponding at least to an amount of fuel for determining a value approximately proportional to the amount of heat given off by the fuel, a second computing circuit responsive to a signal corresponding at least to an amount of feedwater for determining a value approximately proportional to the amount of heat absorbed by the water and the steam, a comparison circuit having inputs connected to respective outputs of the first and second computing circuits, a correction circuit connected between the output of one of the computing circuits and the respective input of the comparison circuit, the correction circuit including a correction member having an output variable only during an operating condition of the steam generator that is not steady-state, the variable output having an effect upon the value of the output of the one computer circuit that is fed to the respective input of the comparison circuit so that, during steady-state operation of the steam generator, the values of the outputs of the computer circuits to the inputs of the comparison circuit are returned as values representing substantially equal amounts of heat for heat given up by the fired fuel and for heat absorbed by the water and the steam.

There are claimed: 
     
       1. Monitoring system for a once-through steam generator for determining deviations between the amount of heat absorbed by the water and the steam of the generator and the amount of heat given off by a firing system for the generator during operating conditions that are not steady-state, as compared to steady-state operation, comprising a first computing circuit responsive to a signal corresponding at least to an amount of fuel for determining a value approximately proportional to the amount of heat given off by the fuel, a second computing circuit responsive to a signal corresponding at least to an amount of feedwater for determining a value approximately proportional to the amount of heat absorbed by the water and the steam, a comparison circuit having inputs connected to respective outputs of said first and second computing circuits, a correction circuit connected between the output of one of said computing circuits and the respective input of said comparison circuit, said correction circuit including a correction member having an output variable only during an operating condition of the steam generator that is not steady-state, said variable output having an effect upon the value of the output of said one computer circuit that is fed to the respective input of said comparison circuit so that, during steady-state operation of the steam generator, the values of the outputs of said computer circuits to the inputs of said comparison circuit are returned as values representing substantially equal amounts of heat for heat given up by the fired fuel and for heat absorbed by the water and the steam. 
     
     
       2. Monitoring system according to claim 1 wherein said comparison circuit for the amounts of heat is a divider. 
     
     
       3. Monitoring system according to claim 1 including a circuit for determining the steady-state operating condition of the steam generator comprising at least one differentiating device having an input connected to a signal source representing a parametric value of the steam generator selected from the group of parametric values consisting of power output and pressure, and a limit value indicator connected to said differentiating device at the load side thereof. 
     
     
       4. Monitoring device according to claim 1 wherein said computer circuits have respective output lines and wherein said correction circuit includes a divider having two inputs respectively connected to said output lines and having an output, said correction member of said correction circuit being a mean value-forming device and having an input connected to said output of said divider, said correction circuit including a multiplier having two inputs respectively connected to said output of said one computer circuit and to said output of said correction member. 
     
     
       5. Monitoring device according to claim 4 wherein said comparison circuit is a divider, and the output of said one computer circuit forms the denominator in the divider of a ratio of the amount of heat given off by the fired fuel to the amount of heat absorbed by the water and the steam. 
     
     
       6. Monitoring device according to claim 1 wherein said comparison circuit is a divider having two inputs and said computer circuits have respective output lines, the output line of one of said computer circuits being connected to one of said divider inputs, said correcting circuit including a multiplier having an output connected to the other input of said divider, said multiplier having two inputs, one of which is connected to the output line of the other of said computer circuits and the other of which is connected to said output of said correcting device of said correcting circuit.